Base station, terminal, band allocation method, and downlink data communication method

ABSTRACT

Provided are a base station, a terminal, a band allocation method, and a downlink data communication method with which bands can be efficiently allocated. In a base station in which a plurality of unit bands can be allocated to a single communication, when a data receiver acquires terminal capability information transmitted by a terminal in the initial access unit band and the bandwidth available for communication indicated by the terminal capability information can accommodate a plurality of unit bands, a unit band group which includes the initial access unit band as well as the unit bands adjacent thereto is allocated to the terminal, and a communication band movement indication, which indicates the movement of the center frequency in the communication band of the terminal toward the center frequency in the unit band group, is transmitted to the terminal using the initial access unit band.

BACKGROUND

1. Technical Field

The present invention relates to a base station, terminal, bandassignment method and downlink data communication method

2. Description of the Related Art

In 3GPP LTE, OFDMA (Orthogonal Frequency Division Multiple Access) isadopted as a downlink communication scheme. In a radio communicationsystem adopting 3GPP LTE, a radio communication base station apparatus(which may be simply referred to as “base station” below) transmits asynchronization channel (“SCH”) or broadcast channel (“BCH”) usingpredetermined communication resources. Then, first, a radiocommunication terminal apparatus (which may be simply referred to as“terminal” below) secures synchronization with the base station bycapturing the SCH. That is, first, the terminal performs a cell search.After that, the terminal obtains parameters unique to the base station(such as a frequency bandwidth) by reading the BCH information (seeNon-Patent Literatures 1, 2 and 3).

Also, standardization of 3GPP LTE-advanced, which realizes fastercommunication than 3GPP LTE, has been started. The 3GPP LTE-advancedsystem (which may be referred to as “LTE+ system” below) follows the3GPP LTE system (which may be referred to as “LTE system” below). In3GPP LTE-advanced, to realize downlink transmission speed equal to orgreater than maximum 1 Gbps, it is expected to adopt a base station andterminal that can perform communication in a wideband frequency equal toor greater than 20 MHz. Here, to prevent unnecessary complication of theterminal, the terminal side is expected to define the terminalcapability related to frequency band support. The terminal capabilitydefines that, for example, the minimum value of support bandwidth is 20MHz.

That is, a base station supporting the LTE+ system (which may bereferred to as “LTE+ base station” below) is formed to be able toperform communication in a frequency band including a plurality of “unitbands.” Here, a “unit band” is a band of a 20-MHz range, including SCH(Synchronization CHannel) near the center, and is defined as a base unitof a communication band. Also, a “unit band” may be expressed as“component carrier(s)” in English in 3GPP LTE.

Also, terminals supporting the LTE+ system (which may be referred to as“LTE+ terminal” below) include a terminal in which acommunication-capable bandwidth can contain only one unit band (whichmay be referred to as “type-1 LTE+ terminal” below) and a terminal inwhich a communication-capable bandwidth can contain a plurality of unitbands (which may be referred to as “type-2 LTE+ terminal” below).

CITATION LIST Non-Patent Literature

-   NPL 1-   3GPP TS 36.211 V8.3.0, “Physical Channels and Modulation (Release    8),” May 2008-   NPL 2-   3GPP TS 36.212 V8.3.0, “Multiplexing and channel coding (Release    8),” May 2008-   NPL 3-   3GPP TS 36.213 V8.3.0, “Physical layer procedures (Release 8),” May    2008

BRIEF SUMMARY Technical Problem

Here, a case is assumed where an LTE+ base station supports an LTE+terminal. FIG. 1 shows an example of mapping SCH and BCH in the LTE+system support base station.

In FIG. 1, a communication bandwidth of the LTE+ base station is 40 MHzand includes two unit bands. Also, SCH and BCH are placed at 20 MHzintervals near the center frequency of each unit band. Here, a nullcarrier for DC offset compensation in a terminal is inserted in thecenter of each frequency band in which SCH and BCH are placed. Also, SCHand BCH are placed in 36 subcarriers each in the higher and lowerfrequency (i.e. a total of 72 subcarriers) from the center of the nullcarrier. Also, physical downlink control channels (“PDCCH's”) are placedin a distributed manner in the whole unit bands.

Similar to a case of the above-noted LTE system, when powered on, theLTE+ terminal first tries capturing an SCH transmitted from the LTE+base station by performing correlation synchronization processing whilemoving the center frequency of the communication band. Upon capturingthe SCH transmitted from the LTE+ base station by peak detection in thecorrelation result, the LTE+ terminal captures a BCH transmitted fromthe LTE+ base station and reads the frequency band of the uplink pairband. Then, the LTE+ terminal starts communicating with the LTE+ basestation by transmitting a signal in PRACH (Physical Random AccessCHannel). Also, a unit band synchronized between the terminal and thebase station may be referred to as “initial access unit band.”

FIG. 2 illustrates an access condition of an LTE+ terminal (i.e. type-2LTE+ terminal) that can perform communication in a communicationbandwidth of 40 MHz, with respect to an LTE+ base station that transmitsSCH and BCH by the mapping method shown in FIG. 1.

As shown in FIG. 2, the type-2 LTE+ terminal adjusts the centerfrequency of that terminal to the SCH frequency position in the initialaccess unit band and receives data signals transmitted from the LTE+base station. Therefore, in spite of being able to receive data signalsin 40 MHz continuous bands, the type-2 LTE+ terminal cannot cover thewhole unit band adjacent to the initial access unit band. That is,actually, communication is performed only in the initial access unitband, and the capability of the LTE+ terminal is not utilized.Therefore, there is a problem that the LTE+ base station cannot assign aband to the type-2 LTE+ terminal efficiently.

FIG. 3 shows another example of mapping SCH and BCH in the LTE+ systemsupport base station.

In FIG. 3, a communication bandwidth of the LTE+ base station is 40 MHzand includes two unit bands. Also, SCH and BCH are placed near thecenter frequency of the communication band.

According to the mapping method in FIG. 3, the LTE+ terminal adjusts thecenter frequency of that terminal to the SCH frequency position, so thatit is possible to cover the whole communication band of the LTE+ basestation by the communication band of that LTE+ terminal.

However, with the mapping method in FIG. 3, SCH and BCH are not mappedon 10 MHz bands at both ends, and, consequently, the LTE+ terminal,which has only 20 MHz terminal capability (i.e. type-1 LTE+ terminal),cannot use the 10 MHz bands at both ends. That is, with the mappingmethod in FIG. 3, frequency is wasted. Therefore, there is a problemthat the LTE+ base station cannot assign a band to the type-1 LTE+terminal efficiently.

FIG. 4 shows another example of mapping SCH and BCH in the LTE+ systemsupport base station.

In FIG. 4, a communication bandwidth of the LTE+ base station is 40 MHzand includes two unit bands. Then, SCH and BACH are placed near thecenter frequency of the communication band and placed near the centerfrequencies of bands of 10 MHz bandwidth from the both ends.

According to the mapping method shown in FIG. 4, the type-1 LTE+terminal can use bands of 10 MHz bandwidth from both ends. However, inthe case where the type-2 LTE+ terminal uses 10 MHz bands at both endsas initial access unit bands, communication is possible only in anarrower band than the case of the mapping method shown in FIG. 2. Thatis, with the mapping method of FIG. 4, there is a problem that the LTE+base station cannot assign a band to the type-2 LTE+ terminalefficiently,

It is therefore an object of the present invention to provide a basestation, terminal, band assignment method and downlink datacommunication method that enable efficient band assignment.

Solution to Problem

The base station of the present invention that can assign a plurality ofunit bands to single communication, employs a configuration having: anobtaining section that obtains terminal capability information which istransmitted by a terminal in an initial access unit band and whichindicates a communication-capable bandwidth of the terminal; and acontrol section that, when the terminal can have the plurality of unitbands in the communication-capable bandwidth indicated by the obtainedterminal capability information, assigns a unit band group including aunit band adjacent to the initial access unit band in addition to theinitial access unit band, to the terminal transmitting the obtainedterminal capacity information, and transmits a communication band movinginstruction to instruct for a reference frequency in a communicationband of the terminal to be moved to a reference frequency in the unitband group, to the terminal using the initial access unit band.

The terminal of the present invention that receives a data signaltransmitted from the above base station in the unit band group assignedfrom the base station, employs a configuration having: a receptionsection that receives the data signal; and a control section that makesthe reception section start receiving the data signal in the initialaccess unit band before a moving process based on the communication bandmoving instruction starts, and continue the reception during a period ofthe moving process and after the period.

The band assignment method of the present invention for assigning a bandused for data communication from a base station to a second terminal ina communication system including the base station that can assign aplurality of unit bands to single communication, a first terminal thatcan have only one unit band in a communication-capable bandwidth and thesecond terminal that can have the plurality of unit bands in acommunication-capable bandwidth, includes: in a terminal, transmittingterminal capability information indicating a communication-capablebandwidth of the terminal in an initial access unit band for the basestation; and, in the base station, when the terminal can have theplurality of unit bands in the communication-capable bandwidth indicatedby the transmitted terminal capability information, assigning a unitband group including a unit band adjacent to the initial access unitband in addition to the initial access unit band, to the terminal, andtransmitting a communication band moving instruction to instruct for areference frequency in a communication band of the assignment targetterminal to be moved to a reference frequency in the unit band group, tothe assignment target terminal using the initial access unit band.

The downlink data communication method of the present inventionincluding the steps of the above band assignment method, includes:starting downlink data communication between the base station and theterminal in the initial access unit band; and in the terminal, movingthe reference frequency in the communication band of the terminal basedon the communication band moving instruction, where the downlink datacommunication starts before a moving process of the reference frequencystarts, and continues during a period of the moving process and afterthe period.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a basestation, terminal, band assignment method and downlink datacommunication method that enable efficient band assignment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of mapping SCH and BCH in an LTE+ system supportbase station;

FIG. 2 illustrates an access condition of an LTE+ terminal that canperform communication in a 40 MHz communication bandwidth, with respectto an LTE+ base station that transmits SCH and BCH by the mapping methodshown in FIG. 1;

FIG. 3 shows another example of mapping SCH and BCH in an LTE+ systemsupport base station;

FIG. 4 shows another example of mapping SCH and BCH in an LTE+ systemsupport base station;

FIG. 5 is a block diagram showing a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 6 is a block diagram showing a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 7 is a sequence diagram showing signal transmission and receptionbetween a terminal and a base station according to Embodiment 1 of thepresent invention;

FIG. 8 illustrates a communication band moved by a terminal according toEmbodiment 1 of the present invention;

FIG. 9 is a block diagram showing a configuration of a terminalaccording to Embodiment 2 of the present invention;

FIG. 10 is a block diagram showing a configuration of a base stationaccording to Embodiment 2 of the present invention;

FIG. 11 is a sequence diagram showing signal transmission and receptionbetween a terminal and a base station according to Embodiment 2 of thepresent invention; and

FIG. 12 illustrates RB formation.

DETAILED DESCRIPTION

Now, embodiments of the present invention will be explained in detailwith reference to the accompanying drawings. Also, in embodiments, thesame components will be assigned the same reference numerals andoverlapping explanation will be omitted.

Embodiment 1

[Terminal configuration] FIG. 5 is a block diagram showing aconfiguration of terminal 100 according to Embodiment 1 of the presentinvention. Terminal 100 is an LTE+ terminal in which thecommunication-capable bandwidth includes a plurality of unit bands. InFIG. 5, terminal 100 is provided with RF receiving section 105, OFDMsignal demodulating section 110, frame synchronization section 115,demultiplexing section 120, broadcast information receiving section 125,PDCCH receiving section 130, PDSCH (Physical Downlink Shared CHannel)receiving section 135, control section 140, RACH (Random Access CHannel)preamble section 145, modulating section 150, SC-FDMA (Single-CarrierFrequency Division Multiple Access) signal forming section 155 and RFtransmitting section 160.

RF receiving section 105 is formed to be able to change a receptionband. RF receiving section 105 receives a center frequency directivefrom control section 140 and, by moving the center frequency based onthis center frequency directive, moves the reception band. RF receivingsection 105 performs radio reception processing (such as down-conversionand analog-to-digital (A/D) conversion) on a radio reception signalreceived in the reception band via an antenna, and outputs the resultingreception signal to OFDM signal demodulating section 110. Also, here,although the center frequency of the reception band is used as areference frequency, it is equally possible to use an arbitraryfrequency included in the reception band as the reference frequency.

OFDM signal demodulating section 110 has CP (Cyclic Prefix) removingsection 111 and fast Fourier Transform (FFT) section 112. OFDM signaldemodulating section 110 receives the reception OFDM signal from RFreceiving section 105. In OFDM signal demodulating section 110, CPremoving section 111 removes a CP from the reception OFDM signal and FFTsection 112 transforms the reception OFDM signal without a CP into afrequency domain signal. This frequency domain signal is outputted toframe synchronization section 115.

Frame synchronization section 115 searches for a synchronization signal(SCH) included in the signal received from OFDM signal demodulatingsection 110 and finds synchronization with base station 200 (describedlater). A unit band included in the found synchronization signal (SCH)is used as the initial access unit band. The synchronization signalincludes a P-SCH (Primary SCH) and S-SCH (Secondary SCH). To be morespecific, frame synchronization section 115 searches for the P-SCH andfinds synchronization with base station 200 (described later).

After finding the P-SCH, frame synchronization section 115 performsblind detection of the S-SCH placed in resources having a predeterminedrelationship with resources in which the P-SCH is placed. By this means,it is possible to find more precise synchronization and obtain the cellID associated with the S-SCH sequence. That is, frame synchronizationsection 115 performs the same processing as in a normal cell search.

Frame synchronization section 115 outputs frame synchronization timinginformation related to the synchronization establishment timing, todemultiplexing section 120.

Demultiplexing section 120 demultiplexes the reception signal receivedfrom OFDM signal demodulating section 110 into the broadcast signal,control signal (i.e. PDCCH signal) and data signal (i.e. PDSCH signal)included in this reception signal, based on the frame synchronizationtiming information. The broadcast signal is outputted to broadcastinformation receiving section 125, the PDCCH signal is outputted toPDCCH receiving section 130, and the PDSCH signal is outputted to PDSCHreceiving section 135. Here, the PDSCH includes individual informationfor a given terminal.

Broadcast information receiving section 125 reads the content of theinput P-BCH (Primary BCH) and obtains information related to the numberof antennas of base station 200 (described later) and downlink systembandwidth. This information is outputted to control section 140.

Broadcast information receiving section 125 receives a D-BCH signalplaced in resources indicated by D-BCH (Dynamic BCH) resource positioninformation (D-BCH frequency position information in this case) includedin the PDCCH signal and extracted in PDCCH receiving section 130, andobtains information included in this received D-BCH signal (e.g.information about the frequency and frequency band of uplink pair bandor PRACH (Physical Random Access CHannel)). This information isoutputted to control section 140. Also, in this specification, anexample case will be explained using frequency as resources.

Based on the decoding directive from control section 140, PDCCHreceiving section 130 extracts information (including the frequencyposition in which the D-BCH is placed, the frequency position in whichthe PDSCH is placed, and uplink frequency allocation information (PDSCHfrequency position information in this case)), included in the PDCCHsignal received from demultiplexing section 120. Out of this extractedinformation, information about the frequency position in which the D-BCHis placed is outputted to broadcast information receiving section 125,information about the frequency position in which the PDSCH is placed isoutputted to PDSCH receiving section 135, and the uplink frequencyallocation information is outputted to SC-FDMA signal forming section155.

PDSCH receiving section 135 extracts a communication band movinginstruction from the PDSCH signal received from demultiplexing section120, based on the information about the frequency position in which thePDSCH is placed, received from PDCCH receiving section 130. Then, theextracted communication band moving instruction is outputted to controlsection 140.

Here, the communication band moving instruction is a directive formoving the center frequency in the communication band of terminal 100 tothe center frequency in the whole unit band group assigned from basestation 200 (described later) to terminal 100 (hereinafter “assignmentunit band group”). Here, in order to reduce the signaling amountrequired for the communication band moving instruction, the centerfrequency of the whole assignment unit band group to adjust in RFreceiving section 105 of terminal 100 is reported as a multiple of 300KHz, which is the lowest common multiple of the downlink subcarrierbandwidth (15 KHz) and the minimum resolution of frequency that can beset by RF receiving section 105 of terminal 100 (100 KHz). This isbecause, when an LTE+ base station transmits a plurality of SCH's usingone IFFT circuit, the interval between SCH's is nothing but an integralmultiple of 15 KHz, and, furthermore, needs to be a multiple of 100 KHzto adjust the center frequency of a reception band for any SCH on theterminal side.

Control section 140 sequentially changes the reception band of RFreceiving section 105 before synchronization is established. Also, aftersynchronization is established and before an RACH preamble istransmitted, control section 140 prepares RACH preamble transmission inthe initial access unit band based on the broadcast signal (P-BCH),control channel (PDCCH) and dynamic broadcast signal (D-BCH) transmittedfrom base station 200 (described later) in the initial access unit bandincluding the frequency position of a synchronization channel. Also,after RACH preamble transmission in the initial access unit band,control section 140 obtains report resource assignment informationreported by the control channel from base station 200 (described later),and transmits terminal capability information of that terminal usingresources indicated by that report resource allocation information. Atthis stage, data communication is possible between base station 200 andterminal 100 in the initial access unit band. Then, control section 140obtains the communication band moving instruction transmitted by basestation 200 according to the terminal capability information, and,first, cuts off downlink data communication and then moves the centerfrequency in the communication band of terminal 100 to the centerfrequency in the whole assignment unit band group based on thecommunication band moving instruction.

Also, after cutting off downlink data communication in the initialaccess unit band, based on a broadcast signal, control channel and LTEdynamic broadcast signal transmitted in a unit band different from theinitial access unit band in the assignment unit band group (hereinafter“additional assignment unit band”), control section 140 prepares RACHpreamble transmission in the additional assignment unit band. Also, uponcompleting the preparation of RACH preamble transmission in theadditional assignment unit band, first, control section 140 cuts offuplink communication between terminal 100 and base station 200(described later) and then transmits the RACH preamble in the additionalassignment unit band. Also, after transmitting the RACH preamble in theadditional assignment unit band, control section 140 obtains the reportresource assignment information reported by the control channel frombase station 200, and using resources indicated by this report resourceassignment information, transmits a communication starting request(aggregation communication starting request) for the whole unit bandgroup assigned by base station 200, to base station 200.

To be more specific, control section 140 identifies PDCCH placementinformation based on the information obtained in broadcast informationreceiving section 125. This PDCCH placement information is uniquelydetermined by the number of antennas of base station 200 (describedlater) and downlink system bandwidth. Control section 140 outputs thePDCCH placement information to PDCCH receiving section 130 and commandsdecoding of a signal placed in the frequency position according to thatinformation.

Also, control section 140 commands RACH preamble section 145 to transmitan RACH preamble according to information included in the D-BCH signalreceived from broadcast information receiving section 125, that is,according to the uplink frequency band and PRACH frequency position.

Also, upon receiving the uplink frequency allocation information fromPDCCH receiving section 130, control section 140 outputs terminalcapability information (i.e. capability information) of that terminal tomodulating section 150 and outputs the uplink frequency allocationinformation to SC-FDMA signal forming section 155. By this means, theterminal capability information is mapped on frequency corresponding tothe uplink frequency allocation information and then transmitted.

Also, based on the communication band moving instruction received fromPDSCH receiving section 135, control section 140 outputs a centerfrequency directive to RF receiving section 105 such that the centerfrequency of the reception band of RF receiving section 105 matches thecenter frequency in the assignment unit band group. Here, controlsection 140 cuts off downlink data communication if the reception bandis subjected to move control based on that communication band movinginstruction.

According to the directive from control section 140, RACH preamblesection 145 outputs an RACH preamble sequence and information related tothe uplink frequency band and PRACH frequency position included in thatdirective, to SC-FDMA signal forming section 155.

Modulating section 150 modulates the terminal capability informationreceived from control section 140 and outputs the resulting modulationsignal to SC-FDMA signal forming section 155.

SC-FDMA signal forming section 155 forms an SC-FDMA signal from themodulation signal received from modulating section 150 and the RACHpreamble sequence received from RACH preamble section 145. In SC-FDMAsignal forming section 155, discrete Fourier transform (DFT) section 156transforms the input modulation signal on the frequency axis and outputsa plurality of resulting frequency components to frequency mappingsection 157. These plurality of frequency components are mapped onfrequency based on the uplink frequency allocation information infrequency mapping section 157 and transformed into a time domainwaveform in IFFT section 158. The RACH preamble sequence is also mappedon frequency based on the uplink frequency allocation information infrequency mapping section 157 and transformed into a time domainwaveform in IFFT section 158. CP attaching section 159 attaches a CP tothe time domain waveform and provides an SC-FDMA signal.

RF transmitting section 160 performs radio transmission processing onthe SC-FDMA signal formed in SC-FDMA signal forming section 155 andtransmits the result via an antenna.

Base Station Configuration

FIG. 6 is a block diagram showing a configuration of base station 200according to Embodiment 1 of the present invention. Base station 200 isan LTE+ base station. In each unit band, base station 200 alwayscontinues to transmit a P-SCH, S-SCH, P-BCH, D-BCH and PDCCHrepresenting frequency scheduling information of D-BCH, in an OFDMscheme. The BCH includes frequency band information, which divides acommunication band every unit band. Therefore, a unit band is alsodefined as a band divided using frequency band information in BCH or aband defined by a distribution width upon placing PDCCH in a distributedmanner.

In FIG. 6, base station 200 is provided with PDCCH generating section205, PDSCH generating section 210, broadcast signal generating section215, modulating section 220, OFDM signal forming section 225, RFtransmitting section 230, RF receiving section 235, CP removing section240, FFT section 245, extracting section 250, RACH preamble receivingsection 255, data receiving section 260 and control section 265. CPremoving section 240, FFT section 245, extracting section 250, RACHpreamble receiving section 255 and data receiving section 260 form anSC-FDMA signal demodulating section.

PDSCH generating section 205 receives uplink frequency allocationinformation for terminal 100 and generates a PDCCH signal including thisuplink frequency allocation information. PDCCH generating section 205masks the uplink frequency allocation information by CRC based on anRACH preamble sequence transmitted from terminal 100, and then includesthe result in the PDCCH signal. The generated PDCCH signal is outputtedto modulating section 220. Here, a sufficient number of RACH preamblesequences are prepared, and the terminal selects an arbitrary sequencefrom these RACH preamble sequences and accesses the base station. Thatis, there is an extremely low possibility that a plurality of terminalsaccess base station 200 at the same time using the same RACH preamblesequence, so that, by receiving a PDCCH subjected to CRC masking basedon that RACH preamble sequence, terminal 100 can detect uplink frequencyallocation information for that terminal without problems.

PDSCH generating section 210 receives a communication band movinginstruction from control section 265 and generates a PDSCH signalincluding this communication band moving instruction. Also, PDSCHgenerating section 210 receives as input transmission data aftertransmission of the communication band moving instruction. Then, PDSCHgenerating section 210 generates a PDSCH signal including the inputtransmission data. The PDSCH signal generated in PDSCH generatingsection 210 is received as input in modulating section 220.

Broadcast signal generating section 215 generates and outputs abroadcast signal to modulating section 220. This broadcast signalincludes P-BCH and D-BCH.

Modulating section 220 forms modulation signals by modulating inputsignals. These input signals include the PDCCH signal, PDSCH signal andbroadcast signal. The formed modulation signals are received as input inOFDM signal forming section 225.

OFDM signal forming section 225 receives as input the modulation signalsand synchronization signals (P-SCH and S-SCH) and forms an OFDM signalin which those signals are mapped on predetermined resources,respectively. In OFDM signal forming section 225, multiplexing section226 multiplexes the modulation signals and the synchronization signals,and IFFT section 227 obtains a time domain waveform by performingserial-to-parallel conversion and then performing an IFFT of themultiplex signal. By attaching a CP to this time domain waveform in CPattaching section 228, the OFDM signal is provided.

RF transmitting section 230 performs radio transmission processing onthe OFDM signal formed in OFDM signal forming section 225 and transmitsthe result via an antenna.

RF receiving section 235 performs radio reception processing (such asdown-conversion and analog-to-digital (A/D) conversion) on a radioreception signal received in a reception band via the antenna, andoutputs the resulting reception signal to CP removing section 240.

CP removing section 240 removes a CP from the reception SC-FDMA signaland FFT section 245 transforms the reception SC-FDMA signal without a CPinto a frequency domain signal.

Extracting section 250 extracts a signal mapped on resourcescorresponding to RACH, from the frequency domain signal received fromFFT section 245, and outputs the extracted signal to RACH preamblereceiving section 255. This extraction of a signal mapped on resourcescorresponding to RACH is always performed so that an LTE+ terminaltransmits an RACH preamble to base station 200 at any timing.

Also, extracting section 250 extracts a signal corresponding to uplinkfrequency allocation information received from control section 265, andoutputs this signal to data receiving section 260. This extracted signalincludes, for example, terminal capability information transmitted byterminal 100 in PUSCH.

First, RACH preamble receiving section 255 transforms the extractedsignal received from extracting section 250 into a single carriersignal. That is, RACH preamble receiving section 255 includes an inversediscrete Fourier transform (IDFT) circuit. Then, RACH preamble receivingsection 255 finds correlation between the resulting single carriersignal and an RACH preamble pattern, and, if the correlation value isequal to or greater than a certain level, decides that an RACH preambleis detected. Then, RACH preamble receiving section 255 outputs an RACHdetection report including pattern information of the detected RACHpreamble (e.g. the sequence number of the RACH preamble) to controlsection 265.

Data receiving section 260 transforms the extracted signal received fromextracting section 250 into a single carrier signal on the time axis andoutputs terminal capability information included in the resulting singlecarrier signal to control section 265. Also, after transmission of thecommunication band moving instruction, data receiving section 260outputs the resulting single carrier signal to a higher layer asreception data.

Upon receiving the RACH detection report from RACH preamble receivingsection 255, control section 265 allocates uplink frequency to terminal100 having transmitted the detected RACH preamble. This allocated uplinkfrequency is used to, for example, transmit terminal capabilityinformation in terminal 100. Then, the uplink frequency allocationinformation is outputted to PDCCH generating section 205.

Also, upon receiving the terminal capability information from datareceiving section 260, control section 265 decides thecommunication-capable bandwidth of the LTE+ terminal based on theterminal capability information. As a result of decision, if thecommunication-capable bandwidth indicated by the terminal capabilityinformation can contain a plurality of unit bands, control section 265allocates a unit band group including a unit band adjacent to theinitial access unit band in addition to the initial access unit band, tothe transmission source terminal of the terminal capacity information(terminal 100 in this case), forms a communication band movinginstruction to instruct for the center frequency in the communicationband of the transmission source terminal to be moved to the centerfrequency in the whole unit band group, and outputs the communicationband moving instruction to PDSCH generating section 210. Here, asdescribed above, this communication band moving instruction includesinformation about the difference from the center frequency position inthe RF receiving section of the RF receiving section of the terminal.This difference information has the value that is an integral multipleof 300 KHz. Similar to normal downlink data, the communication bendmoving instruction is prepared for each terminal in PDSCH generatingsection 210 and then received as input in the modulating section.

Also, after outputting the communication band moving instruction,control section 265 cuts off downlink data communication with terminal100. Then, upon receiving, from RACH preamble receiving section 255, thedetection report of an RACH preamble transmitted in an additionalassignment unit band from terminal 100, control section 265 allocatesuplink frequency to terminal 100. This allocated uplink frequency isused to, for example, transmit terminal capability information interminal 100. Then, the uplink frequency allocation information isoutputted to PDCCH generating section 205.

Also, upon receiving an aggregation communication starting request fromterminal 100, control section 265 starts communicating using the wholeassignment unit band.

Operations of Terminal 100 and Base Station 200

FIG. 7 is a sequence diagram showing signal transmission and receptionbetween terminal 100 and base station 200.

In step S1001, a synchronization signal is transmitted, and cell searchprocessing is performed using this synchronization signal. That is, instep S1001, the reception band of RF receiving section 105 issequentially shifted by control of control section 140, and framesynchronization section 115 searches for a P-SCH. By this means, theinitial synchronization is established. Then, frame synchronizationsection 115 performs blind detection of an S-SCH placed in resourceshaving a predetermined relationship with resources in which the P-SCH isplaced. By this means, it is possible to find more precisesynchronization and obtain the cell ID associated with the S-SCHsequence.

In step S1002 to step S1004, a broadcast signal and control channel aretransmitted and used to prepare RACH preamble transmission in theinitial access unit band.

That is, in step S1002, control section 140 identifies PDCCH placementinformation based on information included in a received D-BCH signal andobtained in broadcast information receiving section 125 (e.g.information about frequency and frequency band of uplink pair band orPRACH (Physical Random Access CHannel)). Then, control section 140outputs the PDCCH placement information to PDCCH receiving section 130and commands decoding of a signal placed in the frequency position basedon the information.

In step S1003, according to the decoding directive from control section140, frequency position information of the D-BCH is extracted in PDCCHreceiving section 130.

In step S1004, based on the D-BCH frequency position information,information included in the received D-BCH signal (e.g. informationabout frequency and frequency band of uplink pair band or PRACH(Physical Random Access CHannel)) is extracted in broadcast informationreceiving section 125.

In step S1005, under control of control section 140, RACH preamblesection 145 transmits an RACH preamble using the uplink frequency bandand PRACH frequency position obtained in step S1002.

In step S1006, control section 265 of base station 200 having receivedthe RACH preamble allocates uplink frequency to terminal 100 havingtransmitted the RACH preamble, and transmits uplink frequency allocationinformation to that terminal 100.

In step S1007, control section 140 of terminal 100 having received theuplink frequency allocation information transmits terminal capabilityinformation of that terminal, using the uplink frequency.

At this stage, base station 200 and terminal 100 are in conditions wherecommunication is possible, and, in step S1008, data communication startsbetween base station 200 and terminal 100.

In step S1009, if the communication-capable bandwidth indicated by thereceived terminal capability information can contain a plurality of unitbands, control section 265 of base station 200 allocates a unit bandgroup including a unit band adjacent to the initial access unit band inaddition to the initial access unit band, to terminal 100 of theterminal capacity information, and transmits a communication band movinginstruction to instruct for the center frequency in the communicationband of terminal 100 to be moved to the center frequency in the wholeunit band group.

First, in step S1010, terminal 100 having received this communicationband moving instruction cuts off downlink data communication and thenmoves the center frequency in the communication band to the centerfrequency in the whole assignment unit band group based on thecommunication band moving instruction.

FIG. 8 illustrates the communication band moved in terminal 100.

As shown in the left side of FIG. 8, in step S1001 to step S1009, thecenter frequency of the communication band of terminal 100 matches theSCH frequency position in unit band A of the initial access unit band.In this condition, as explained using FIG. 2, the capability of terminal100 is not utilized.

By contrast with this, by moving the center frequency of thecommunication band of terminal 100 in step S1010, as shown in the rightside of FIG. 8, it is possible to contain the whole assignment unit bandgroup in the communication band of terminal 100. Also, the width of eachunit band is the same in FIG. 8, and therefore the center frequency ofthe communication band of terminal 100 matches the boundary frequencybetween unit band A and unit band B.

Referring back to the flow of FIG. 7, in step S1011 to step S1013, abroadcast signal and control channel are transmitted and used to prepareRACH preamble transmission in an additional assignment unit band.

Upon completing the preparation of the RACH preamble in the additionalassignment unit band, control section 140 cuts off uplink communicationbetween terminal 100 and base station 200 in step S1014, and transmitsthe RACH preamble in the additional assignment unit band in step S1015.

In step S1016, control section 265 of base station 200 having receivedthe RACH preamble allocates uplink frequency to terminal 100 havingtransmitted the RACH preamble in the additional assignment unit band,and transmits uplink frequency allocation information to that terminal100.

In step S1017, control section 140 of terminal 100 transmits anaggregation communication starting request using resources indicated bythe uplink frequency allocation information transmitted from basestation 200 in step S1016.

Upon receiving this aggregation communication starting request, controlsection 265 of base station 200 starts communicating using the wholeassignment unit band group.

As described above, according to the present embodiment, in base station200 in which a plurality of unit bands can be assigned in singlecommunication, data receiving section 260 obtains terminal capabilityinformation transmitted by terminal 100 in the initial access unit band,and, when the communication-capable bandwidth indicated by that terminalcapability information can contain a plurality of unit bands, assigns aunit band group including a unit band adjacent to the initial accessunit band in addition to the initial access unit band, to terminal 100,and transmits a communication band moving instruction to instruct forthe center frequency in the communication band of terminal 100 to bemoved to the center frequency in that unit band group, to terminal 100using the initial access unit band.

By this means, it is possible to contain the whole assignment unit bandgroup in the communication band of terminal 100. That is, base station200 that allows efficient band assignment for terminal 100 is realized.

Also, in the above explanation, the reference frequency of the receptionband of terminal 100, the reference frequency of a unit band (i.e. SCHfrequency position) and the reference frequency of an assignment unitband group have been explained as respective center frequencies.However, the present invention is not limited to this, and it is equallypossible to use other frequency positions as the reference frequency. Anessential requirement is that each reference frequency is determinedsuch that the whole unit band is contained in the reception band ofterminal 100 by adjusting the reference frequency of the reception bandof terminal 100 to the reference frequency of the unit band and thewhole assignment unit band group is contained in the reception band ofterminal 100 by adjusting the reference frequency of the reception bandof terminal 100 to the reference frequency of the assignment unit bandgroup.

Embodiment 2

In Embodiment 1, when a terminal transmits an RACH preamble in anadditional assignment unit band, RF frequency has to be switched to anuplink pair band corresponding to the additional assignment unit band,and, consequently, communication is momentarily cut off (i.e. conditionin which an ACK to uplink data and downlink data cannot be transmitted)in the communication system. By contrast with this, in Embodiment 2, itis possible to realize a communication system in which efficient bandassignment is possible without cutting off communication momentarily.Now, a terminal and base station forming this communication system willbe explained.

FIG. 9 is a block diagram showing a configuration of terminal 300according to Embodiment 2. In FIG. 9, terminal 300 has control section310.

In control section 310, control processing from synchronizationestablishment to data communication between base station 200 andterminal 100 in the initial access unit band, is the same as the controlprocessing in control section 140 of terminal 100 according toEmbodiment 1.

Control section 310 obtains a communication band moving instructiontransmitted according to terminal capability information from basestation 400 (described later), and, based on this communication bandmoving instruction, moves the center frequency in the communication bandof terminal 300 to the center frequency in the whole assignment unitband group. At this time, data communication between base station 400and terminal 300 started in the initial access unit band before thecenter frequency moving process, is not cut off.

Here, base station 400 (described later) transmits the communicationband moving instruction and all of the content of P-BCH transmitted inan additional assignment unit band (i.e. the content of MIB (MasterInformation Block)). To be more specific, the MIB includes the extensionof PDCCH in the frequency axis direction (downlink frequency bandwidth),the number of antennas of the base station in the move destination band(i.e. the number of antennas to transmit a reference signal) and thenumber of OFDM resources used for others than PDCCH (e.g. a responsesignal to an uplink data signal). Further, base station 400 transmitsthe communication band moving instruction and information related to theSCH position and null carrier position in the additional assignment unitband.

Therefore, based on the obtained MIB, control section 310 obtains acontrol channel and LTE dynamic broadcast signal in the additionalassignment unit band. Here, although terminal 100 according toEmbodiment 1 performs, for example, RACH preamble transmission in theadditional assignment unit band, terminal 300 does not perform thatprocessing.

Upon obtaining the control channel and D-BCH (i.e. SIB (SystemInformation Block)) in the additional assignment unit band, controlsection 310 transmits a read completion report of the SIB to basestation 400 using an uplink pair band of the initial access unit band.This SIB read completion report is used as an aggregation communicationstarting request.

FIG. 10 is a block diagram showing a configuration of base station 400according to Embodiment 2 of the present invention.

In FIG. 10, base station 400 has control section 410.

When the communication-capable bandwidth indicated by terminalcapability information can contain a plurality of unit bands, controlsection 410 assigns a unit band group including a unit band adjacent tothe initial access unit band in addition to the initial access unitband, to the transmission source terminal of the terminal capabilityinformation (terminal 300 in this case), forms a communication bandmoving instruction to indicate the center frequency in the communicationband of the transmission source terminal to be moved to the centerfrequency in the whole unit band group, and outputs the communicationband moving instruction to PDSCH generating section 210. Also, controlsection 410 outputs the communication band moving instruction, thecontent of MIB and information related to the SCH position and nullcarrier position, to PDSCH generating section 210.

FIG. 11 is a sequence diagram showing signal transmission and receptionbetween terminal 300 and base station 400.

The sequence diagram of FIG. 11 and the sequence in FIG. 7 are the samein step S1001 to step S1008.

In step S2001, when the communication-capable bandwidth indicated byreceived terminal capability information can contain a plurality of unitbands, control section 410 of base station 400 assigns a unit band groupincluding a unit band adjacent to the initial access unit band inaddition to the initial access unit band, to terminal 300 of theterminal capacity information, and transmits a communication band movinginstruction to instruct for the center frequency in the communicationband of terminal 300 to be moved to the center frequency in the wholeunit band group. Further, control section 410 transmits thecommunication band moving instruction, the content of MIB andinformation related to the SCH position and null carrier position in theadditional assignment unit band.

Terminal 300 having received the communication band moving instructionmoves the center frequency in the communication band to the centerfrequency in the whole assignment unit band group, based on thecommunication band moving instruction. At this time, data communicationbetween base station 200 and terminal 100 started before the centerfrequency moving process in the initial access unit band, is not cutoff. That is, reception of a downlink data signal in the initial accessunit band starts before a moving process based on the communication bandmoving instruction starts, and this reception continues during themoving process period and after the end of this period.

After that, upon obtaining the control channel and D-BCH (i.e. SIB(System Information Block)) in the additional assignment unit band basedon the MIB, control section 310 of terminal 300 transmits an aggregationcommunication starting request to base station 400 using an uplink pairband of the initial access unit band (step S2002).

As described above, according to the present embodiment, terminal 300starts receiving a data signal in the initial access unit band before amoving process based on a communication band moving instruction starts,and continues the reception during the moving process period and afterthe end of this period. That is, communication in the initial accessunit band is not cut off momentarily.

Also, according to the present embodiment, in base station 400, controlsection 410 transmits information used to identify a control channeltransmitted in an additional assignment unit band, together with acommunication band moving instruction in the initial access unit band.

By this means, terminal 300 needs not receive a P-BCH in the additionalassignment unit band, so that it is possible to start aggregationcommunication earlier than in the case of Embodiment 1.

Also, in the above explanation, the reference frequency of the receptionband of terminal 300, the reference frequency of a unit band (i.e. SCHfrequency position) and the reference frequency of an assignment unitband group have been explained as respective center frequencies.However, the present invention is not limited to this, and it is equallypossible to use other frequency positions as the reference frequency. Anessential requirement is that each reference frequency is determinedsuch that the whole unit band is contained in the reception band ofterminal 300 by adjusting the reference frequency of the reception bandof terminal 300 to the reference frequency of the unit band and thewhole assignment unit band group is contained in the reception band ofterminal 300 by adjusting the reference frequency of the reception bandof terminal 300 to the reference frequency of the assignment unit bandgroup.

Also, in the above explanation, MIB information of an additionalassignment band is reported from base station 400 to terminal 300.However, the present invention is not limited to this, and base station400 may report only the difference between MIB in the initial accessunit band and MIB in the additional assignment unit band. By this means,it is possible to reduce the signaling amount.

Also, in the above explanation, MIB information is transmitted with acommunication band moving instruction. However, the present invention isnot limited to this, and it is equally possible to perform broadcastingto all terminals using, for example, the D-BCH of each unit band. Bythis means, at the stage of step S1004, terminal 300 can obtain MIBinformation in an additional assignment unit band.

Also, an aggregation communication starting request is not alwaystransmitted by a PUCCH in the initial access unit band. For example,base station 400 may transmit the aggregation communication startingrequest by a certain specific RACH preamble in the initial access unitband.

Other Embodiment

(1) Here, an index attached to a resource block (RB) used as a base unitin scheduling and so on, will be explained.

In Embodiment 2, terminal 300 receives a communication band movinginstruction, SCH position, null carrier position and the MIB content ineach unit band, from base station 400.

Here, as described above, the center frequency of the communication bandof terminal 300 is moved to a position different from the position ofSCH placed near the center of each unit band. That is, it follows that anull carrier is present in a position different from the center positionof a frequency band in which an SCH is placed.

Each RB is formed with a certain number of carriers without nullcarriers. Therefore, terminal 300 needs to redefine RB's usinginformation obtained from base station 400.

Therefore, first, with the system frequency bandwidth read from the SCHposition and MIB content in a certain unit band, terminal 300 virtuallycalculates the extension of PDCCH in the unit band.

Next, terminal 300 checks whether or not a null carrier is present inother positions than the SCH center in the unit band. As a result, ifthere is a null carrier in a position apart from the SCH center,terminal 300 forms an RB using twelve subcarriers excluding the nullcarrier in the same way as other null carriers.

FIG. 12 illustrates an RB form. NC1 in FIG. 12 represents a null carrierthat is present in a position different from the SCH center. As shown inFIG. 12, similar to other null carriers, the null carrier that ispresent in a position different from the SCH center is removed from theRB-forming subcarriers to form RB's.

Here, the extension of PDCCH is set in RB units. Then, the number ofRB's included in the PDCCH corresponds to the system frequency bandwidthon a one-to-one basis.

Therefore, terminal 300 recalculates the PDCCH extension calculatedvirtually (in RB units), taking into account the null carrier that ispresent in the position different from the SCH center, and determinesthe frequency band in which a PDCCH is finally placed.

(2) Although example cases have been described above with Embodiments 1to 4 where the present invention is implemented with hardware, thepresent invention can be implemented with software.

Furthermore, each function block employed in the description of each ofEmbodiments 1 to 4 may typically be implemented as an LSI constituted byan integrated circuit. These may be individual chips or partially ortotally contained on a single chip. “LSI” is adopted here but this mayalso be referred to as “IC,” “system LSI,” “super LSI,” or “ultra LSI”depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be regenerated is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2008-201006, filed onAug. 4, 2008, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The base station, terminal, band assignment method and downlink datacommunication method of the present invention are effective to allowefficient band assignment.

The invention claimed is:
 1. An integrated circuit comprising:communication circuitry, which, in operation, controls receivinginformation including both: (i) first information related to a referencefrequency of a communication band, the communication band including afirst component carrier and a second component carrier added to thefirst component carrier, in which a synchronization signal is mappedaround a center of each of the first component carrier and the secondcomponent carrier, and (ii) second information used for determining thesecond component carrier, said information including both the firstinformation and the second information being received in the firstcomponent carrier on a Physical Downlink Shared Channel (PDSCH), andcontrol circuitry, which, in operation, controls setting the referencefrequency of the communication band based on the first information, toacquire a Physical Downlink Control Channel (PDCCH) in the secondcomponent carrier based on the second information, and to performcommunication simultaneously on the first component carrier and thesecond component carrier, wherein the second information includes adownlink frequency bandwidth of the second component carrier, a numberof antennas for use in the second component carrier, and resources usedto receive a response signal in the second component carrier responsiveto an uplink data signal.
 2. The integrated circuit according to claim1, comprising: at least one input coupled to the communicationcircuitry, wherein the at least one input, in operation, inputs data;and at least one output coupled to the communication circuitry, whereinthe at least one output, in operation, outputs data.
 3. The integratedcircuit according to claim 1, wherein the communication circuitry, inoperation, initiates reception of downlink data signal on the firstcomponent carrier prior to setting of the reference frequency based onthe first information.
 4. The integrated circuit according to claim 1,wherein the receiving includes receiving a message that includes thefirst information and the second information.
 5. The integrated circuitaccording to claim 1, wherein the first component carrier is a componentcarrier used for communication between a user equipment and a basestation apparatus before the reference frequency is set.
 6. Theintegrated circuit according to claim 1, wherein the reference frequencyrelates to a center frequency of the first component carrier and acenter frequency of the second component carrier.
 7. The integratedcircuit according to claim 1, wherein a maximum bandwidth of each of thefirst component carrier and the second component carrier is 20 MHz. 8.The integrated circuit according to claim 1, wherein a bandwidth of eachof the first component carrier and the second component carrier is equalto or less than 20 MHz.
 9. The integrated circuit according to claim 1,wherein a maximum bandwidth of the communication band including thefirst component carrier and the second component carrier is over 20 MHz.10. The integrated circuit according to claim 2, wherein the at leastone output and the at least one input, in operation, are coupled to anantenna.
 11. An integrated circuit comprising: at least one input,which, in operation, inputs data; and circuitry, which is coupled to theat least one input and which, in operation: controls reception ofinformation including both: (i) first information related to a referencefrequency of a communication band, the communication band including afirst component carrier and a second component carrier added to thefirst component carrier, in which a synchronization signal is mappedaround a center of each of the first component carrier and the secondcomponent carrier, and (ii) second information used for determining thesecond component carrier, said information including both the firstinformation and the second information being received in the firstcomponent carrier on a Physical Downlink Shared Channel (PDSCH), andsets the reference frequency of the communication band based on thefirst information, to acquire a Physical Downlink Control Channel(PDCCH) in the second component carrier based on the second information,and to perform communication simultaneously on the first componentcarrier and the second component carrier, wherein the second informationincludes a downlink frequency bandwidth of the second component carrier,a number of antennas for use in the second component carrier, andresources used to receive a response signal in the second componentcarrier responsive to an uplink data signal.
 12. The integrated circuitaccording to claim 11, further comprising: at least one output coupledto the circuitry, wherein the at least one output, in operation, outputsdata.
 13. The integrated circuit according to claim 11, wherein thecircuitry, in operation, initiates reception of downlink data signal onthe first component carrier prior to setting the reference frequencybased on the first information.
 14. The integrated circuit according toclaim 11, wherein the circuitry, in operation, controls reception of amessage that includes the first information and the second information.15. The integrated circuit according to claim 11, wherein the firstcomponent carrier is a component carrier used for communication betweena user equipment and a base station apparatus before the referencefrequency is set.
 16. The integrated circuit according to claim 11,wherein the reference frequency relates to a center frequency of thefirst component carrier and a center frequency of the second componentcarrier.
 17. The integrated circuit according to claim 11, wherein amaximum bandwidth of each of the first component carrier and the secondcomponent carrier is 20 MHz.
 18. The integrated circuit according toclaim 11, wherein a bandwidth of each of the first component carrier andthe second component carrier is equal to or less than 20 MHz.
 19. Theintegrated circuit according to claim 11, wherein a maximum bandwidth ofthe communication band including the first component carrier and thesecond component carrier is over 20 MHz.
 20. The integrated circuitaccording to claim 12, wherein the at least one output and the at leastone input, in operation, are coupled to an antenna.